THE IMPENETRABLE SEA 



Imagine the glove-finger instantaneously restored to its 

 normal position, and you have the action which takes 

 place as the tiny tubes shoot out. The tiny thread-like 

 barbs can be used only once. After they are discharged 

 they are replaced with new ones. 



We have seen that the barbs are released by triggers 

 which operate when stimulated in two ways — by contact 

 and by chemical action. The most extraordinary fact 

 about the man-of-war is that the process is not strictly 

 automatic. For the fishes which swim in and out among 

 the tentacles, and are apparently given permission to do 

 so by the man-of-war, continually brush against the 

 triggers — yet they are not released. This implies that the 

 man-of-war has some kind of control over the chemical 

 stimuli of the triggers and can restrain their action. 



Besides its ''fighting units", the man-of-war has "indi- 

 viduals" which perform very different duties. Some are 

 flask-shaped bodies which do nothing but eat. Others, 

 resembling clusters of small berries, are continually occu- 

 pied in producing more and more eggs, to develop into 

 more and more ''ships" for the "fleet". Other organisms 

 are solely occupied in repairing any damage caused to 

 the "vessel". There are also organisms which control the 

 man-of-war's speed and direction. 



The man-of-war is a "ship" that sails — propelled by 

 wind-power. It has a huge float (the "sail") extending 

 along its upper surface. The "hull" itself is much larger 

 and blunter at the stern, to which all the tentacles and 

 organisms of the "ship" are attached, leaving the "bow" 

 free to force its way through the water. The sail has a 

 shell-like appearance. The course of the "ship" is steered 

 by the longest tentacles — which lie outside the others. 

 They serve as living rudders, for they trail backward as 

 the vessel moves, acting as a controllable "brake" or 

 "drag" on the vessel's movement. If the wind impelling 

 the vessel forward is too strong, the rudder-like streamers 

 are lengthened considerably, reducing its speed. If there 



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